A reproducing system is produced for reproducing music recorded on a digital disc, and a rotating dial is provided to be rotated by a user. A light emitting window 11 of the light source is constituted of a collection of a plurality of point light sources and has a shape which meets a predetermined expression. The tests are performed with several frequencies and the channels with the least micro-reflections are identified. Suitable adhesion promoting agents include nitrogen, nitrogen-containing compounds, carbon-containing compounds, carbon and nitrogen containing compounds, silicon-containing compounds, silicon and carbon containing compounds, silicon, carbon, and nitrogen containing compounds, or mixtures thereof. According to the invention, the motor control device can be adjusted according to a characteristic curve of the electric motor andor of the fan, and thereby the power andor rotational speed of the electric motor can be adjusted.